Assessments of traumatic brain injury (TBI), including concussion, and other neurocognitive deficits may be assisted through ocular function testing. Concussion and other TBI can lead to changes in brain function, and variations in higher cortical brain functions such as vision may reveal underlying trauma. The visual system of the human involves roughly half of the brain's neurological circuits, and concussions and other TBIs frequently result in abnormalities in ocular functions, such as convergence (the turning inward of the eyes separately to focus on a near-field object), accommodation (the changing of the shape of the eye to alter lens shape for near-field and far-field focus), the vestibular-ocular reflex (VOR, the stabilization of focus during head movement), ocular muscle balance (alignment of the eyes), saccades (quick simultaneous movements of both eyes between two or more phases of fixation), and pursuit (the ability to follow a moving object). Ocular function testing during concussion assessment may include, for example the testing of eye tracking capability (e.g., smooth pursuit and saccade), and convergence and accommodation.
Further, the ocular function testing may include a strabismus test. Strabismus refers to a disorder in which the eyes do not look in exactly the same direction at the same time. For example, one eye may look straight ahead, while the other eye turns inward, outward, upward, or downward. Different methods may be used to test strabismus, including a light reflex testing and a cover testing.
Prior art ocular assessment techniques are either not suited for field deployment such as a sports sideline or a battlefield, or else are imprecise due to their manual nature. For example, large instruments, such as autorefractors and wavefront aberrometers, can measure refractive changes in the eye, but are not suited for field deployment. Imaging the surface of the eye using axial biometry or biomicroscopy is also not suited for use in non-specialized settings. Phoropter testing for accommodation requires a controlled environment and can take 15 minutes or longer. Similarly, eye-tracking manual testing techniques may include paper-and-pencil based forms, including for example vestibular-ocular motor screening (VOMS)), saccades test cards.
The above-mentioned conventional manual testing techniques suffer from many drawbacks. For example, manual near-point convergence and near-point accommodation tests are generally conducted by using a target for the subject to focus on, for example, a tongue depressor, which is moved towards and away from the subject. The subject identifies the point at which he or she notices a pre-identified visual event, such as the loss of focus of the target, a distortion in vision, the acquisition of focus, etc. Alternatively, for a near point of convergence test, a clinician may observe the subject's eyes and identify a loss of convergence, for example, as drifting of one eye. A complaint by clinicians is that these tests are subjective, inexact, and performed inconsistently. The distance measurements are prone to error because they require the person performing them (often but not always a physician) to hold the tongue depressor fixed in space while simultaneously trying to measure the distance to the subject. Measures such as the starting distance from the subject, the rate of movement of the target toward the subject, etc., can be difficult to control and measure in real time, resulting in inconsistencies and imprecision in performance and results. While imprecision is detrimental to accurate assessment of TBI including concussion, these drawbacks have the natural result of inhibiting adoption of these methods, depriving some routine assessments of a visual modality altogether.
The exemplary systems and methods disclosed herein are directed to addressing one or more of the problems set forth above during psychophysical ocular assessments and/or other deficiencies in the prior art.